The present invention relates to a system and method for detecting faults in an electric motor.
Small, low cost electric motors and controllers are used in certain product applications, such as electric reel drives on greens mowers which includes a 3-phase permanent magnet brushless DC electric motor. The motor controller typically includes high power FETs which can be damaged by overheating or overcurrents. It is difficult to detect when such a motor fails, and when a system with such a failed motor is not working, a repair technician may attempt to repair the system by replacing the controller instead of the faulty motor. But, if the motor was faulty, it may merely damage the new controller. Thus, it is desired to have a means for detecting motor faults before the faulty motor can damage a controller.
Typically, systems for detecting faults in such motors have been complicated and have required expensive circuitry. U.S. Pat. No. 6,381,110, issued to Nagashima et al. in 2002, describes a system for detecting isolation or coil-to-case faults of a motor. However, this system cannot detect inductance degradation or phase coil-to-phase coil short circuit faults.